In order to monitor the gas composition in a gas mixture such as the amount of hydrocarbons in air in a production facility or the gas composition in reactor systems gas sensors are utilized being positioned in chosen locations to monitor the gas composition and/or detect chosen gases. Traditionally these sensors have been limited by the fact that they require power and communication connections, which make installation expensive, make it difficult to move or add sensors and limits the possible locations of the sensors.
Thus there is a need for a gas sensor which can be operated without power supply and communication lines. Long maintenance intervals for fixed gas detectors require long battery lifetime. Reliability of gas sensors requires short response time and thus frequent or continuous measurement. Earlier technology for reliable gas sensors was not capable of providing wireless monitoring with long battery lifetime and short response time because of the high energy consumption it required.
A gas sensor with lower energy consumption will also be an advantage in portable gas detectors, enabling smaller battery pack and/or longer battery life.
One proposed solution is described in Norwegian patent 327678 (see also WO 2009/011593) where two sensors are used. The first sensor is a non-specific sensor with low energy consumption which detects changes in the concentration of one or more gasses in the environment. The second sensor is specific but has higher energy consumption. When the first sensor detects a change in the gas concentration it activates the second sensor so as to detect whether there is an increase in the concentration of one specific gas. This solution results in an energy consumption being significantly less than would be the case if the second sensor was active continuously.
A related solution is described in US2010/0089122 where a gas sensor monitors a gas in a mixture and where the detection of the gas starts by pulsing a heat source in order to increase the accuracy of a quantitative measurement of the gas. The heating is in this case for avoiding saturation problems in the sensor cell but a hibernation method is used for saving energy. However, the energy consumption is still too high to be used in a solitary sensor.